The invention relates to a dilatation catheter for treating a constricted blood vessel. Dilatation catheters have been employed for some time in the treatment of vascular obstructions generally known as angioplasty. Such catheters have an elongated tubular body with a balloon at the distal end that is inflatable and deflatable under fluid pressure. A guide wire is typically first inserted within the vessel to the location of the constriction. The catheter is then inserted (with the balloon deflated) over the guide wire with the balloon positioned at the location of the constriction. By way of an externally accessible internal lumen leading through the support tube, the balloon is filled with fluid, so that it expands causing the occluding tissue to be pressed outwardly into the vessel wall.
A disadvantage of the angioplasty procedure is that the treatment of severe constrictions takes a comparatively long time and can require periodic interruption in order to avoid distal ischemia. It has also been found that the treatment is sometimes unsuccessful because the occluding tissue is not removed but merely pressed to the wall of the vessel and restenosis can eventually occur. The success of such a treatment can be improved if a substance that will dissolve the impairing tissue, as for example a plasminogen activator, is introduced into the vessel to be treated.